scholarly journals Element abundances of unevolved stars in the open cluster M 67

2006 ◽  
Vol 450 (2) ◽  
pp. 557-567 ◽  
Author(s):  
S. Randich ◽  
P. Sestito ◽  
F. Primas ◽  
R. Pallavicini ◽  
L. Pasquini
Keyword(s):  
Open Cluster ◽  
Element Abundances

Selecting a Photometric System for Gaia: C, N, O and Alpha-Process Elements

2003 ◽  
Vol 12 (4) ◽  
Author(s):  
G. Tautvaišienė ◽  
B. Edvardsson ◽  
S. Bartašiūtė
Keyword(s):  
Open Cluster ◽  
Stellar Atmospheres ◽  
Photometric System ◽  
Mixing Processes ◽  
Stellar Spectra ◽  
Element Abundances ◽  
Carbon And Nitrogen ◽  
Spectral Changes ◽  
Process Elements ◽  
Process Element

AbstractThe sensitivity of stellar spectra to C, N, O and α-process element abundances is discussed with the aim of taking this effect into account when selecting a photometric system for the Gaia orbiting observatory. On the basis of a spectrometric, photometric and theoretical study of spectra of evolved first-ascent giants and clump stars in the open cluster NGC 7789 it is demonstrated that evolutionary alterations of carbon and nitrogen abundances can cause noticeable spectral changes and, if not taken into account, may yield misleading photometric [Fe/H] determinations. Carbon features in stellar atmospheres show a particularly complex behavior being dependent on mixing processes in stars, on the stellar surface gravity and on the abundance of oxygen which can also be altered by different reasons. NH bands could serve for the evaluation of mixing processes in stars and the interpretation of carbon dominated spectral regions. Abundances of α-process elements can be evaluated photometrically by using the direct indicators - Ca II H and K lines and Mg I b triplet.

scholarly journals Element abundances in the metal-rich open cluster NGC 6253

2007 ◽  
Vol 465 (1) ◽  
pp. 185-196 ◽  
Author(s):  
P. Sestito ◽  
S. Randich ◽  
A. Bragaglia
Keyword(s):  
Open Cluster ◽  
Element Abundances

scholarly journals Chemical composition of giant stars in the open cluster IC 4756

2018 ◽  
Vol 615 ◽  
pp. A165 ◽  
Author(s):  
Vilius Bagdonas ◽  
Arnas Drazdauskas ◽  
Gražina Tautvaišienė ◽  
Rodolfo Smiljanic ◽  
Yuriy Chorniy
Keyword(s):  
Chemical Elements ◽  
Open Cluster ◽  
Theoretical Models ◽  
Open Clusters ◽  
Galactic Chemical Evolution ◽  
Element Abundances ◽  
Giant Stars ◽  
Thin Disc ◽  
The Mean ◽  
Red Giant

Context. Homogeneous investigations of red giant stars in open clusters contribute to studies of internal evolutionary mixing processes inside stars, which are reflected in abundances of mixing-sensitive chemical elements like carbon, nitrogen, and sodium, while α- and neutron-capture element abundances are useful in tracing the Galactic chemical evolution. Aims. The main aim of this study is a comprehensive chemical analysis of red giant stars in the open cluster IC 4756, including determinations of 12C∕13C and C/N abundance ratios, and comparisons of the results with theoretical models of stellar and Galactic chemical evolution. Methods. We used a classical differential model atmosphere method to analyse high-resolution spectra obtained with the FEROS spectrograph on the 2.2 m MPG/ESO Telescope. The carbon, nitrogen, and oxygen abundances, 12C∕13C ratios, and neutron-capture element abundances were determined using synthetic spectra, and the main atmospheric parameters and abundances of other chemical elements were determined from equivalent widths of spectral lines. Results. We have determined abundances of 23 chemical elements for 13 evolved stars and 12C∕13C ratios for six stars of IC 4756. The mean metallicity of this cluster, as determined from nine definite member stars, is very close to solar – [Fe/H] = − 0.02 ± 0.01. Abundances of carbon, nitrogen, and sodium exhibit alterations caused by extra-mixing: the mean 12C∕13C ratio is lowered to 19 ± 1.4, the C/N ratio is lowered to 0.79 ± 0.05, and the mean [Na/Fe] value, corrected for deviations from the local thermodynamical equilibrium encountered, is enhanced by 0.14 ± 0.05 dex. We compared our results to those by other authors and theoretical models. Conclusions. Comparison of the α-element results with the theoretical models shows that they follow the thin disc α-element trends. Being relatively young (~ 800 Myr), the open cluster IC 4756 displays a moderate enrichment of s-process-dominated chemical elements compared to the Galactic thin disc model and confirms the enrichment of s-process-dominated elements in young open clusters compared to the older ones. The r-process-dominated element europium abundance agrees with the thin disc abundance. From the comparison of our results for mixing-sensitive chemical elements and the theoretical models, we can see that the mean values of 12C∕13C, C/N, and [Na/Fe] ratios lie between the model with only the thermohaline extra-mixing included and the model which also includes the rotation-induced mixing. The rotation was most probably smaller in the investigated IC 4756 stars than 30% of the critical rotation velocity when they were on the main sequence.

scholarly journals Chemical abundances of open clusters from high-resolution infrared spectra – II. NGC 752

2019 ◽  
Vol 491 (1) ◽  
pp. 544-559
Author(s):  
G Böcek Topcu ◽  
M Afşar ◽  
C Sneden ◽  
C A Pilachowski ◽  
P A Denissenkov ◽  
...  
Keyword(s):  
High Resolution ◽  
Near Infrared ◽  
Open Cluster ◽  
Light Element ◽  
Open Clusters ◽  
Evolutionary Stage ◽  
Chemical Abundance ◽  
Chemical Abundances ◽  
Element Abundances ◽  
Solar Metallicity

ABSTRACT We present a detailed near-infrared chemical abundance analysis of 10 red giant members of the Galactic open cluster NGC 752. High-resolution (R ≃ 45000) near-infrared spectral data were gathered with the Immersion Grating Infrared Spectrograph, providing simultaneous coverage of the complete H and K bands. We derived the abundances of H-burning (C, N, O), α (Mg, Si, S, Ca), light odd-Z (Na, Al, P, K), Fe-group (Sc, Ti, Cr, Fe, Co, Ni), and neutron-capture (Ce, Nd, Yb) elements. We report the abundances of S, P, K, Ce, and Yb in NGC 752 for the first time. Our analysis yields solar-metallicity and solar abundance ratios for almost all of the elements heavier than the CNO group in NGC 752. O and N abundances were measured from a number of OH and CN features in the H band, and C abundances were determined mainly from CO molecular lines in the K band. High-excitation $\rm{C\,\small {I}}$ lines present in both near-infrared and optical spectra were also included in the C abundance determinations. Carbon isotopic ratios were derived from the R-branch band heads of first overtone (2−0) and (3−1) 12CO and (2−0) 13CO lines near 23 440 Å and (3−1) 13CO lines at about 23 730 Å. The CNO abundances and 12C/13C ratios are all consistent with our giants having completed ‘first dredge-up’ envelope mixing of CN-cyle products. We independently assessed NGC 752 stellar membership from Gaia astrometry, leading to a new colour–magnitude diagram for this cluster. Applications of Victoria isochrones and MESA models to these data yield an updated NGC 752 cluster age (1.52 Gyr) and evolutionary stage indications for the programme stars. The photometric evidence and spectroscopic light element abundances all suggest that the most, perhaps all of the programme stars are members of the helium-burning red clump in this cluster.

Heavy-Element Abundances of the Old Open Cluster NGC 6791

1998 ◽  
Vol 502 (1) ◽  
pp. L39-L43 ◽  
Author(s):  
Ruth C. Peterson ◽  
Elizabeth M. Green
Keyword(s):  
Heavy Element ◽  
Open Cluster ◽  
Element Abundances

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

Radial Velocities, Binarity, and Kinematic Membership in the Open Cluster NGC 2516

2000 ◽  
Vol 119 (5) ◽  
pp. 2296-2302 ◽  
Author(s):  
Jorge Federico González ◽  
Emilio Lapasset
Keyword(s):  
Open Cluster ◽  
Radial Velocities

Heavy‐Element Abundances in Blue Compact Galaxies

1999 ◽  
Vol 511 (2) ◽  
pp. 639-659 ◽  
Author(s):  
Yuri I. Izotov ◽  
Trinh X. Thuan
Keyword(s):  
Heavy Element ◽  
Element Abundances ◽  
Compact Galaxies

scholarly journals Formation rate of LB-1-like systems through dynamical interactions

2020 ◽  
Vol 72 (3) ◽  
Author(s):  
Ataru Tanikawa ◽  
Tomoya Kinugawa ◽  
Jun Kumamoto ◽  
Michiko S Fujii
Keyword(s):  
Open Cluster ◽  
Formation Rate ◽  
Open Clusters ◽  
Type Star ◽  
Dynamical Mechanism ◽  
Milky Way Galaxy ◽  
Triple Systems ◽  
Stellar Collisions ◽  
Solar Metallicity ◽  
Helium Star

Abstract We estimate formation rates of LB-1-like systems through dynamical interactions in the framework of the theory of stellar evolution before the discovery of the LB-1 system. The LB-1 system contains a ∼70 ${M_{\odot}}$ black hole (BH), a so-called pair instability (PI) gap BH, and a B-type star with solar metallicity, and has nearly zero eccentricity. The most efficient formation mechanism is as follows. In an open cluster, a naked helium star (with ∼20 ${M_{\odot}}$) collides with a heavy main sequence star (with ∼50 ${M_{\odot}}$) which has a B-type companion. The collision results in a binary consisting of the collision product and the B-type star with a high eccentricity. The binary can be circularized through the dynamical tide with radiative damping of the collision product envelope. Finally, the collision product collapses to a PI-gap BH, avoiding pulsational pair instability and pair instability supernovae because its He core is as massive as the pre-colliding naked He star. We find that the number of LB-1-like systems in the Milky Way galaxy is ∼0.01(ρoc/104 ${M_{\odot}}$ pc−3), where ρoc is the initial mass densities of open clusters. If we take into account LB-1-like systems with O-type companion stars, the number increases to ∼0.03(ρoc/104 ${M_{\odot}}$ pc−3). This mechanism can form LB-1-like systems at least ten times more efficiently than the other mechanisms: captures of B-type stars by PI-gap BHs, stellar collisions between other types of stars, and stellar mergers in hierarchical triple systems. We conclude that no dynamical mechanism can explain the presence of the LB-1 system.

Sign in / Sign up

Export Citation Format

Share Document